How much power might the creator of the first Artificial General Intelligence obtain?
"Artificial Intelligence" has existed for many, many years.  Decades even.  Go back to Arthur Samuel and his Checkers playing program (if not before).  That's AI.

The thing is, as soon as computers can do something, people want to quit treating it as AI.  AI is almost, by definition, something that can't really exist, because it has to be about something humans can do, that computers can't.   So all progress made in the field is reclassified as "not AI" as soon as it does anything useful.

A more salient question might be "who will be the first to announce that Artificial General Intelligence" has been created.   AGI will, if it ever happens, be fundamentally different in terms of being able to learn to do anything, as opposed to, say, a Checkers program which can only play Checkers, or a Go program that can only play Go, etc.

And the answer to that question is -- nobody knows.  Nobody even know for sure that AGI will ever happen (though a lot of us presume that it will).  Anyway, there isn't a ton of research on AGI going on, relative to the amount of research in Machine Learning / Narrow AI.  But somebody working in their garage could make a huge breakthrough tomorrow for all we know.  I think a lot of people assume that creating this will take Nation-State level resources, but that hasn't really been proven.  So it might be some kid in a garage in Omaha tomorrow, or it might be the Chinese government in 2074.  There's just no way to really know.